The change in the Republican leadership team also gave new duties to Chief Deputy Majority Whip Eric Cantor of Virginia and Rules Committee Chairman David Dreier of California.

“It’s a big opportunity now,” said Rep. Jack Kingston, Georgia Republican. He said the party must show voters that it still can cut spending and “get that vote on immigration our constituents have been asking for in every town meeting in the last two years.”

Rep. Joe Pitts, Pennsylvania Republican and head of the Values Action Team, said conservatives had relied on Mr. DeLay’s ability to fight on many fronts, and they will learn whether Mr. Blunt can push their agenda as effectively, particularly in conference committees.

“We’ve worked with him well, but he hasn’t been in that key position,” Mr. Pitts said.

Mr. Blunt will be tested to see whether he can preserve a conscience clause in a House-passed spending bill to protect health care providers who refuse to participate in abortions, and whether he can have a House-Senate conference remove a hate-crimes amendment that was attached to another bill.

Rep. Dave Weldon, Florida Republican, said Mr. DeLay took the lead in rallying votes to defeat an alternative stem-cell bill pushed by Democrats and moderate Republicans that conservative pro-life members opposed.

“Nobody is going to be exactly like Tom DeLay,” Mr. Weldon said, but “Roy Blunt is a good, solid conservative that I can support.”

Both conservatives and moderates said Mr. Blunt brings a different style but that the agenda this year has been established, with Hurricane Katrina spending, appropriations and perhaps Social Security as priorities.

“I don’t think there is going to be one iota of difference,” said Rep. Michael N. Castle, Delaware Republican.

“House Republicans have a well-laid-out agenda already that Mr. Blunt will be working to schedule,” said Burson Taylor, Mr. Blunt’s spokeswoman. She said the acting majority leader sees his role as temporary and expects major decisions about scheduling to be made as a team with House Speaker J. Dennis Hastert, Illinois Republican, leading the way.

She also said she expects Mr. DeLay to continue to be a guiding light for conservatives.

“No one expects that advocacy to stop because he’s not, temporarily, the majority leader,” she said.

Conservatives said Mr. Blunt’s voting record is similar to Mr. DeLay’s and are watching to see if he is willing to step into the occasional fight with the White House.

That will probably matter most on immigration, where the president is pushing for a guest-worker program and Mr. DeLay instead focusing on a law-enforcement bill.

Rep. Tom Tancredo, the Colorado Republican who has become a leader in calling for immigration enforcement, is not certain what will happen.

Although he thinks Mr. Blunt will support an enforcement bill first, the White House pressure will be intense.

“I don’t know if he will go to the wall on that as I think maybe DeLay would,” Mr. Tancredo said.

Conservative activists said they don’t expect a change in party direction.

“For the core issues of the majority, I clearly see it will be the same,” said Family Research Council President Tony Perkins, noting in particular pro-life and fiscal issues. “Is he the hardball player that Tom DeLay is? I don’t know. He hasn’t had to be because Tom DeLay has filled that role. But I have great confidence in Roy Blunt.”

Mr. DeLay is accused of conspiring to use corporate donations to support candidates to the Texas Legislature, a violation of state law. Mr. DeLay says the indictment is a partisan attack by Democratic District Attorney Ronnie Earle.